Comparisons of glenoid bony defects between normal cadaveric specimens and patients with recurrent shoulder dislocation: an anatomic study

Background The location and degree of bony defects that can affect clinical outcomes remains controversial in recurrent shoulder dislocation. The purpose of this study was to define the most common location of glenoid bony defects in patients with recurrent shoulder dislocation. Materials and methods We analyzed the shape and aspect ratio of 44 glenoids from deceased donors. Glenoid size was analyzed using a 3-dimensional (3D) computed tomography (CT) scan in 24 patients with recurrent shoulder dislocation who underwent arthroscopic Bankart repair. We measured the distances from the center of the longitudinal axis of the glenoid to the anterior glenoid rim at 9 positions, 10° apart, from 3:00 to 6:00 o'clock positions in the cadaver and patient groups. We compared the quantification of glenoid defects in the 24 patients using the 3D CT scan. A predictive model based on a discriminant analysis was developed. Results The largest length differences of the glenoid were at the 3:20 o'clock position. When percentage of bone antidefect of the 3:20 o'clock position was used, the model predicted the existence of a defect with 89.7% hit ratio. Conclusions The major direction of the glenoid defect was in a more anterior position rather than the anteroinferior glenoid in patients with recurrent shoulder dislocation. The 3:20 o'clock position was most common location of glenoid defect in shoulder instability. This pattern of bone loss should be considered by the surgeon when operating on these patients, especially when performing arthroscopic procedures for Bankart repair or bone block operations to the glenoid.